The present invention relates to apparatuses and methods adapted to scrub thin substrates or wafers such as semiconductor wafers, compact discs, glass substrates, and the like. More particularly, the present invention relates to the rotational rate of a scrubber brush.
During formation of a semiconductor device, various layers (e.g. oxides) require planarization to remove steps or undulations prior to formation of subsequent layers. Planarization is typically performed mechanically by forcing a semiconductor wafer face down against a semi-porous polishing pad which is saturated with an abrasive compound (i.e., a slurry) and by rotating the polishing pad relative to the semiconductor wafer. The slurry reacts with the wafer""s surface, which makes the surface easier to remove, and the rotary motion between the polishing pad and the wafer mechanically removes layers of the intermediate oxide and is continued until the oxide steps or undulations are removed.
After polishing, slurry residue is conventionally cleaned or scrubbed from the wafer surfaces via mechanical scrubbing devices, which may employ polyvinyl acetate (PVA) brushes, brushes made from other porous or sponge-like material, or brushes made with nylon bristles, etc. Although conventional scrubbing devices may remove the majority of slurry and other particulates from a wafer""s surfaces, some residual slurry and particulates may remain following wafer scrubbing and streaks may be found on the wafer""s surface.
Accordingly, a need remains for an improved method and apparatus adapted to clean semiconductor wafers (and other similar substrates).
The present inventors have discovered that streaking and particle generation occurs when, after cleaning is complete, a scrubber brush""s rotational speed is slowed while the scrubber brush is in contact with the wafer. Such reduction in speed is conventionally employed to reduce fluid spray/splashing that may otherwise occur due to the scrubber brush""s higher rotational speed. Such spray and splashing is undesirable because the scrubber enclosure door conventionally opens (allowing wafer handler entry) before the scrubber brush is removed from the wafer""s surface and thus allows wafer extraction to occur more quickly. The open door may allow fluid spray to exit the scrubber chamber.
Accordingly, the present invention provides methods and apparatuses that may remove slurry residue and other particles from a wafer""s surface more effectively than does a conventional scrubber device. In a first aspect, the inventive method may comprise rotating a scrubber brush at a non-reduced rate, while the scrubber brush is in contact with the wafer, and removing the scrubber brush from contact with the wafer while rotating the scrubber brush at the non-reduced rate. It will be understood that the non-reduced rate is a rate employed to clean the wafer, and that the non-reduced rate is not a slower or reduced rate such as conventionally employed prior to removing a scrubber brush from contact with a wafer.
In a second aspect, the inventive method may comprise providing a scrubber brush adapted to scrub a wafer, rotating the scrubber brush at a non-reduced rate, while the scrubber brush is in contact with the wafer, removing the scrubber brush from contact with the wafer while rotating the scrubber brush at the non-reduced rate, and slowing the rotation of the scrubber brush from the non-reduced rate to a second rate after removing the scrubber brush from contact with the wafer while simultaneously or subsequently opening the scrubber""s enclosure door.
The inventive apparatus comprises a mechanism adapted to support a wafer, a scrubber brush adapted to contact a wafer supported by the wafer supporting mechanism, a motor adapted to rotate the scrubber brush, a mechanism adapted to move the scrubber brush into and out of contact with a wafer supported by the wafer supporting mechanism, and a controller coupled to the motor and to the mechanism adapted to move the scrubber brush. The controller contains a program adapted to perform the following steps: rotating the scrubber brush at a non-reduced rate while the scrubber brush is in contact with the wafer, and removing the scrubber brush from contact with the wafer while rotating the scrubber brush at the non-reduced rate. In one aspect, the scrubber brush rotates only at the non-reduced rate when in contact with the wafer. In a further aspect the apparatus may also comprise a chamber enclosure having a door, and the controller program may be adapted to slow the scrubber brush""s rotational rate after the scrubber brush is removed from contact with the wafer, while simultaneously or subsequently opening the chamber door.
Other features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.